The invention relates generally to sensor systems, and more particularly to a microwave-based or radio frequency (RF) based sensor system for measuring a clearance between two objects through a standing wave null detection technique.
Various types of sensors have been used to measure the distance between two objects. In addition, these sensors have been used in various applications. For example, a turbine has a number of turbine blades that are disposed adjacent to a shroud. The clearance between one of the turbine blades and the shroud varies depending on the temperature of the turbine region. It is desirable that a gap or clearance between the turbine blades and the shroud be maintained for safe and efficient operation of the turbine. A sensor may be disposed within the turbine to measure the distance between the turbine blades and the shroud. The distance may be used to direct movement of the shroud to maintain the desired displacement between the shroud and the turbine blades.
In certain applications, a microwave-based sensor is employed to measure the distance between two objects. Such sensors exhibit an impedance, which varies with the relative physical position of the adjacent objects. Typically, the impedance is determined based upon phase and magnitude measurements of an incident and a reflected signal from the sensor. Unfortunately, existing measurement techniques for measuring the phase and magnitude of the incident and the reflected signals can be relatively inaccurate. Further, such measurement systems require high complexity electronics in order to make accurate measurements. Incorporation of such electronics and other processing requirements is a challenge due to costs, power consumption, size and added complexity involved in such processing requirements.
Accordingly, a need exists for providing a sensor system that provides an accurate measurement of clearance between two objects by employing a relatively simpler, robust and cost-effective measurement technique. It would also be advantageous to provide a sensor system that could be employed for accurate clearance measurement by minimizing the effect of calibration drift and noise in a system.